Solvent refining of mineral oil



Patented Nov. 1, i938 UNITED STATES 'PATENT OFFICE SOLVENT DEFINING F OIL Ren de M. Taveau, Beacon, Louis A. Clarke, Fishkill, and Robert E. Manley, Beacon, N. Y., assignors to The Texas Company, New.York, N. Y., a corporation of Delaware No Drawing. Application July 5, 1934,

Serial No. 733,864

2 Claims. (c1. 196 13l This invention relates to refining mineral oil We have found it advantageous to remove the with solvents for the production of lubricating asphaltic constituents from oil prior to extraction oils. with funural. Furfural tends to extract the The invention contemplates the production of naphthenic constituents from the oil in prefer- 5 lubricating oil from mixed base crudes and the ence to the asphaltic bodies and consequently, 5

like containing asphaltic, naphthenic and parafin the case of certain oils which are rich in 'as finic constituents, including wax, by a process phaltic material, the 011, after extraction with involving treatment of the oil with a solvent furfural, may still contain substantial amounts adapted to separate and remove the asphaltic of undesirable asphaltic matter. The presence bodies, extraction of the de-asphaltized oil with of this asphaltic matter, however, tends to in- 10 a solvent adapted to separate and remove the terfere with the desired selective action of the naphthenic constituents of low lubricating value, furfural. Consequently, by removing the asand thereafter dewaxing this refined oil. phaltic bodies from. the oil prior to extraction The invention contemplates carrying out the with furfural, the latter solvent is used to greater l5 successive steps for the removal of asphaltic eifect so that the naphthenic bodies can be more and naphthenic bodies from the oil through the efficiently extracted from the oil. Accordingly, medium of a common solvent in conjunction with the combination of alcohol treatment for the re-. a suitable extraction solvent of the character of moval of asphaltic bodies, followed by furfural furiural. A common solvent suitable for this extraction to, remove the naphthenic constitu- 2 purpose is one which is adapted to precipitate ents, provides a suitable method for refining the asphaltic constituents while maintaining the heavy residual oils derived from mixed base remaining oil in solution, and which is also crudes, and which contain substantial amounts of adapted to serve as a diluent during the subseasphaltic material. quent extraction and, if desired, dewaxing step. Furthermore, the presence of the alcohol in We have found that'asuitable solvent for this the 011 during subsequent extraction with fur- 25 purpose comprises a solventselected from the 'fural serves to bring about a more effective and group of aliphatic alcohols containing up to seven intimate contact between the furfural and the carbon atoms, their isomers, mixtures thereof, 011, due to t e diluent e e o e including mixtures of the isomers with the nor- I In the case a of certain types of oil, aliphatic mal alcohols. alcohols possess certain desirable modifying ef- 30 The invention therefore comprises mixing on fects upon the selective action of furfural. For containing asphaltic, naphthenic and paraflinic p 061158-111 highly Pammnic Oils h as constituents with an aliphatic alcohol, or a mixv may be derived from Pennsylvania Crude are ture of aliphatic alcohols of the above character relatively insoluble in fulfllml, and the undein sufficient proportion to precipitate all or a sub- 'sirable constituents of low lubricating value may 35 stantial portion of the asphaltic constituents be diflicult of removal. Amyl 81 if Present while retaining the remaining oil in solution. Su ta-ble proportions with the furfural serves The precipitated asphaltic constituents are then as a DID-Solvent e y tending o c ease e removed from the dilute mixture, following which solubility effect of furfural for the oil constituents 40 the dilute mixtureis subjected to extraction with Iof low lubricating va and us facilitating 40 an extractive solvent of the character of furfural. their e va in the extract y Other extractive solvents, such as acetone, nitro n t other ham! w certain other types of benzene, etc., may be employed instead of furoil furfural possesses certain desirable modifyiural, although furfural is preferred since a mixing effects upon the deasphaltizing action of aliture of aliphatic alcohol with furfural provides phat c alco ols. For example, certain oils such 45 a very eifective mixture for extracting mixed base as Mid-Continent Residuum are diflicult to deoils to separate therefrom a maximum yield of asphaltize because of the relatively high soluoil having the desired lubricating qualities. bility of the asphaltic constiuents in amyl alcohol.

We are aware that certain of the aliphatic al- Furfural if present in suitable proportions with cohols have been employedin the prior artherethe alcohol serves as an anti-solvent thereby 50 tofore for the purpose of removingasphaltic contending to decrease the solubility effect of the alstituents from mineral oil. It is novel, however, cohol for the aspl .altic constituents, and thus fato employ such alcohols in conjunction with an cilitate their removal in the insoluble asphaltic extractive solvent ofthe character of furi'ural layer.

for the purpose of pacticing our invention. Lubricating oil as prepared by subjecting crude 55 the favorable solvent efiect of the alcohol on batch or by countercurrent operation.

such constituents, they are removed in the raffinate layer and thereby enhance the quality of raffinate.

Our invention is adapted to the treatment of wax-bearing oil" when employing certain of the aliphatic alcohols as, for example, amyl alcohol as the common solvent. Since amyl alcohol, under certain conditions of temperature and dilution, may tend to precipitate some of the waxy constituents, the latter will be precipitated along with the asphaltic bodies and thus decrease the amount of wax to be removed in the subsequent treatment of the oil.

However, when treating wax-bearing oil containing substantial amounts of wax, the rafiinate may contain substantial proportions of the wax. In that case dewaxing may be readily effected since the mixture is already in a dilute condition and contains substantial amounts of furfural or extraction solvent which, in itself, provides an anti-solvent for the wax. If desired, additional qualities of diluent and anti-solvent may be added thereto to further facilitate the removal of wax, which may be accomplished by the usual mechanical means involving filtration, centrifuging and cold settling.

An important advantage of our invention resides in effecting the removal of asphaltic and naphthenic bodies prior to dewaxing since, in many instances, these bodies or the colloidal substances associated therewith, tend to inhibit complete separation between oil and wax. The presence of these materials also impedes removal of the separated wax from the oil, particularly in the case of dewaxing by filtration.

In the practice of our invention for the treatment of a heavy residual cylinder stock fraction derived from mixed base crudes, the oil may be.

mixed in a ratio of about one volume of oil to four or five volumes of alcohol. The alcohol comprises preferably butyl alcohol, amyl alcohol or a. mixture of butyl and isopropyl alcohol. The mixture is maintained at a temperature of about F. or F. or at a temperature high enough to keep the wax in solution. Sufficient pressure is employed to maintain the alcohol in a liquid state at the temperatures employed.

The temperature selected, as well as the proportion of the alcohol, will depend upon the nature of the oil undergoing treatment. If the temperature is too high, a substantial amount of the asphalt may remain dissolved in the oil. On the other hand, if the temperature is too low substantial amounts of oil may be separated along with the asphalt.

The treatment with alcohol may be effected in The asphaltic material may be separated from the mixture of oil and alcohol by settling or centrifuging. We have found that centrifuging proves a very effective method of removing the precipitated asphaltic bodies. If desired the mixture may be subjected to settling into layers and the asphaltic layer then subjected to settling.

Afterremo'val of the insoluble asphaltic constituents, all or part of the alcohol may be stripped from the resulting de-asphaltized 011. For example. sufllcient of the alcohol may'be it acts as a modifying solvent and diluent. By

virtue of its diluent efiect, it permits more effective contact between furfural'and oil and also more rapid settling and separation into layers.

The extraction with furfural may also be carried out in either batch or countercurrent operation.

Where the oil undergoing treatment contains wax, the resulting raflinate or paraffinic fraction will contain substantial amounts of wax and it is therefore necessary to subject the mixture to dewaxing. To facilitate dewaxing, further quantities of alcohol may be' added, if necessary, in order to increase the extent of dilution. The mixture already contains some furfural which serves as a wax anti-solvent. Additional quantities of wax anti-solvent liquid may be added, if desired.

The resulting mixture is then chilled to temperatures of the order of 10 F. whereupon the wax is solidified. The cold mixture may then be centrifuged, filtered or settled in order to separate and remove the wax. Where it is filtered it may advantageously be filtered in the presence of a suitable filter-aidmaterial such as Filter Cel,

fullers earth, diatomaceous earth, or the like.

The solvents contained in the filtrate and wax may be removed by distillation or in ny other suitable manner and recovered for reu e.

The invention is not restricted to the particular operating condiitons mentioned above. The temperatures as well as the solvent proportions set forth may be varied depending on the nature of the oil undergoing treatment.

The invention is not limitedto the treatment of residual lubricating oil fractions, as above described, but is also adapted to the treatment of distillate lubricating fractions.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are pended claims.

We claim:

1. In the refining of heavy residual wax-bearing mineral lubricating oil stock derived from Mid-Continent crude, the method comprising mixing the oil with a mixture of isopropyl alcohol, butyl alcohol and furfural in an amount sufficient to precipitate asphaltic constituents of oil while retaining remaining constituents of the oil in solution, removing the asphaltic constituents from the mixture of oil and solvent, extracting the mixture of oil and solvent with a further quantity of furfural, forming an extract phase containing low viscosity index constituents of a rafiinate phase containing highuviscosity index constituents and wax, mixing additional furfural and alcohol with the raflinate phase such that the solvent mixture has selective action as between oil and wax, chilling the mixture to a temperature of around 0 F. and below to precipitate wax, and removing the wax so precipitated.

indicated in the ap- 2. The method of removing, asphalt from heavy residual wax-bearing oil at a temperature in the range 120 to 150 F. and substantially above the temperature at which waxy constituents of the oil become solid which comprises subjecting the oil to countercurrent contact with a substantially non-aqueous mixture of isopropyl alcohol; butyl alcohol and extraction solvent having the essential selective action of Iurtural as between naphthenic and paraflinic constituents of oil in proportion such that the alcoholic mixture has substantially no solvent action on the asphaltic constituents and substantially complete solvent action on the non-asphaltic constituents of the oil, forming an asphaltic phase comprising asphaltic constituents mixed with a small amount of solvent, and a non-asphaltic phase comprising non-asphaltic constituents dissolved in the bulk of the solvent, separating the two phases, extracting the non-asphaltic phase with a further quantity of extraction solvent to remove low viscosity index constituents thereby producing a raflinate phase of high viscosity index containing wax, and dewaxing the raflinate phase in the presence of the extraction solvent and a further quantity of alcohol such that the solvent mixture has selective action as between oil and wax at the dewaxing temperature.

RENE in: M. TAVEAU.

LOUIS A. CLARKE. ROBERT E. MANLEY. 

